Theoretical Modeling for Hepatic Microwave Ablation

Thermal tissue ablation is an interventional procedure increasingly being used for treatment of diverse medical conditions. Microwave ablation is emerging as an attractive modality for thermal therapy of large soft tissue targets in short periods of time, making it particularly suitable for ablation of hepatic and other tumors. Theoretical models of the ablation process are a powerful tool for predicting the temperature profile in tissue and resultant tissue damage created by ablation devices. These models play an important role in the design and optimization of devices for microwave tissue ablation. Furthermore, they are a useful tool for exploring and planning treatment delivery strategies. This review describes the status of theoretical models developed for microwave tissue ablation. It also reviews current challenges, research trends and progress towards development of accurate models for high temperature microwave tissue ablation

Nested Helmholtz coil design for producing homogeneous transient rotating magnetic fields

Citation: Podaru, G., Moore, J., Dani, R. K., Prakash, P., & Chikan, V. (2015). Nested Helmholtz coil design for producing homogeneous transient rotating magnetic fields. Review of Scientific Instruments, 86(3), 6. doi:10.1063/1.4908173Electromagnets that can produce strong rotating magnetic fields at kHz frequencies are potentially very useful to exert rotating force on magnetic nanoparticles as small as few nanometers in size. In this article, the construction of a pulsed high-voltage rotating electromagnet is demonstrated based on a nested Helmholtz coil design. The energy for the coils is provided by two high-voltage discharge capacitors. The triggered spark gaps used in the experiments show sufficient accuracy to achieve the high frequency rotating magnetic field. The measured strength of the rotating magnetic field is 200 mT. This magnetic field is scalable by increasing the number of turns on the coils, by reducing the dimensions of the coils and by increasing the discharge current/voltage of the capacitors. (C) 2015 AIP Publishing LLC

TricycloDNA-modified oligo-2′-deoxyribonucleotides reduce scavenger receptor B1 mRNA in hepatic and extra-hepatic tissues—a comparative study of oligonucleotide length, design and chemistry

We report the evaluation of 20-, 18-, 16- and 14-mer phosphorothioate (PS)-modified tricycloDNA (tcDNA) gapmer antisense oligonucleotides (ASOs) in Tm, cell culture and animal experiments and compare them to their gap-matched 20-mer 2′-O-methoxyethyl (MOE) and 14-mer 2′,4′-constrained ethyl (cEt) counterparts. The sequence-matched 20-mer tcDNA and MOE ASOs showed similar Tm and activity in cell culture under free-uptake and cationic lipid-mediated transfection conditions, while the 18-, 16- and 14-mer tcDNA ASOs were moderate to significantly less active. These observations were recapitulated in the animal experiments where the 20-mer tcDNA ASO formulated in saline showed excellent activity (ED50 3.9 mg/kg) for reducing SR-B1 mRNA in liver. The tcDNA 20-mer ASO also showed better activity than the MOE 20-mer in several extra-hepatic tissues such as kidney, heart, diaphragm, lung, fat, gastrocnemius and quadriceps. Interestingly, the 14-mer cEt ASO showed the best activity in the animal experiments despite significantly lower Tm and 5-fold reduced activity in cell culture relative to the 20-mer tcDNA and MOE-modified ASOs. Our experiments establish tcDNA as a useful modification for antisense therapeutics and highlight the role of chemical modifications in influencing ASO pharmacology and pharmacokinetic properties in animal

A Novel Pipeline for Adrenal Gland Segmentation: Integration of A Hybrid Post-Processing Technique with Deep Learning

Accurate segmentation of adrenal glands from CT images is essential for enhancing computer-aided diagnosis and surgical planning. However, the small size, irregular shape, and proximity to surrounding tissues make this task highly challenging. This study introduces a novel pipeline that significantly improves the segmentation of left and right adrenal glands by integrating advanced pre-processing techniques and a robust post-processing framework. Utilising a 2D UNet architecture with various backbones (VGG16, ResNet34, InceptionV3), the pipeline leverages test-time augmentation (TTA) and targeted removal of unconnected regions to enhance accuracy and robustness. Our results demonstrate a substantial improvement, with a 38% increase in the Dice similarity coefficient for the left adrenal gland and an 11% increase for the right adrenal gland on the AMOS dataset, achieved by the InceptionV3 model. Additionally, the pipeline significantly reduces false positives, underscoring its potential for clinical applications and its superiority over existing methods. These advancements make our approach a crucial contribution to the field of medical image segmentation

Progress and Challenges towards a Standard Approach for Dielectric Measurement and Reporting of Biological Tissues

The dielectric properties of biological tissues play a crucial role in shaping the development, implementation, safety evaluation and viability of microwave-based medical technologies. With the growing global exploration of electromagnetic-based technologies as solutions for many different clinical needs and challenges, ensuring accurate, interpretable, and re-usable data of dielectric properties of tissues is of high importance. This paper provides a comprehensive overview of the endeavors undertaken by a collaborative working group to establish standardized approaches for measuring the dielectric properties of tissues.</p

Multilayered broadband antenna for compact embedded implantable medical devices: design and characterization

Design and characterization of a multilayered compact implantable broadband antenna for wireless biotelemetry applications is presented in this paper. The main features of this novel design are miniaturized size, structure that allows integration of electronic circuits of the implantable medical device inside the antenna, and enhanced bandwidth that mitigates possible frequency detuning caused by heterogeneity of biological tissues. Using electromagnetic simulations based on the finite-difference timedomain method, the antenna geometry was optimized to operate in the 401-406 MHz Medical Device Radio communications service band. The proposed design was simulated implanted in a muscle tissue cuboid phantom and implanted in the arm, head, and chest of a high-resolution whole-body anatomical numerical model of an adult human male. The antenna was fabricated using low-temperature co-fired ceramic technology. Measurements validated simulation results for the antenna implanted in muscle tissue cuboid phantom. The proposed compact antenna, with dimensions of 14 mm × 16 mm × 2 mm, presented a −10 dB bandwidth of 103 MHz and 92 MHz for simulations and measurements, respectively. The proposed antenna allows integration of electronic circuit up to 10 mm × 10 mm × 0.5 mm. Specific absorption rate distributions, antenna input power, radiation pattern and the transmission channel between the proposed antenna and a half-wavelength dipole were evaluated

Current Status and Emerging Techniques for Measuring the Dielectric Properties of Biological Tissues

The dielectric properties of biological tissues are key parameters that support the design and usability of a wide range of electromagnetic-based medical applications, including for diagnostics and therapeutics, and allow the determination of safety and health effects due to exposure to electromagnetic fields. While an extensive body of literature exists that reports on values of these properties for different tissue types under different measurement conditions, it is now evident that there are large uncertainties and inconsistencies between measurement reports. Due to varying measurement techniques, limited measurement validation strategies, and lack of metadata reporting and confounder control, reported dielectric properties suffer from a lack of repeatability and questionable accuracy. Recently, the American Society of Mechanical Engineers (ASME) Thermal Medicine Standards Committee was formed, which included a Tissue Properties working group. This effort aims to support the translation and commercialization of medical technologies, through the development of a standard lexicon and standard measurement protocols. In this work, we present initial results from the Electromagnetic Tissue Properties subgroup. Specifically, this paper reports a critical gap analysis facing the standardization pathway for the dielectric measurement of biological tissues. All established measurement techniques are examined and compared, and emerging ones are assessed. Perspectives on the importance and challenges in measurement validation, accuracy calculation, metadata collection, and reporting are also discussed

Development and Characterization of 3-Dimensional Cell Culture Models of Adrenocortical Carcinoma

Adrenocortical carcinoma (ACC) is a rare malignancy of the adrenal cortex that is associated with a poor prognosis. Developing effective treatment options for ACC is challenging owing to the current lack of representative preclinical models. This study addressed this limitation by developing and characterizing 3-dimensional (3D) cell cultures incorporating the ACC cell lines, MUC-1, HAC15, and H295R in a type I collagen matrix. ACC tissue samples were analyzed by immunohistochemistry to determine the presence of type I collagen in the tumor microenvironment. Cell viability and proliferation were assessed using flow cytometry and confocal microscopy. mRNA expression of steroidogenic enzymes and steroid secretion was analyzed by comparing the 3D and monolayer cell culture models. All cells were successfully cultured in a type I collagen matrix, which is highly expressed in the ACC tumor microenvironment and showed optimal viability until day 7. All 3 models showed increased metabolic and proliferative activity over time. Three-dimensional cell cultures were steroidogenic and demonstrated increased resistance to the gold standard chemotherapy, mitotane, compared with monolayer. The use of these models may lead to an improved understanding of disease pathology and provide a better representative platform for testing and screening of potential therapies